If you want to print on plastic, it’s challenging – most plastics are chemically inert and non-porous. That means you can apply all the ink you want; it’s not going to stick. In the 1950’s, a Danish engineer named Verner Eisby experimented with various techniques to overcome these challenges. He found that exposing the surface to be printed on to gas flame or sparks modified the surface to improve adhesion with the ink. It did so, though, in a crude & uneven manner, leaving imperfections & inconsistencies in the printed product. He then tried applying a high frequency corona discharge in a linear array. The plasma (gas in an ionized state) generated left a homogeneously treated surface on which to print, smoothly & evenly.
This has become the “industry standard” for many of the labels we see on commercial products, from shampoo & wine bottles on the grocery store shelf, to pennants & banners at public events. It also leaves the surface even more prone to picking up a static charge from rolling or unrolling, stacking, sliding, etc.
One of our customers makes a great many labels for all kinds of these commercial products, and uses an EXAIR Gen4 Ionizing Bar immediately prior to the printing operation:
Model 8024 24″ Gen4 Ionizing Bar removes static from Corona treated plastic label film.
EXAIR Corporation has a variety of Static Eliminator Products to fit most any industrial or commercial application. If you’d like to find out more, give me a call.
Russ Bowman
Application Engineer
EXAIR Corporation
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A company that made credit cards was having issues in their print quality, and static was the culprit. They used PVC sheets as a base material to print on, and like with any non-conductive materials, static can be generated easily and create problems. For this company, static was attracting dirt to the surface of the material, causing blemishes in the print. They contacted EXAIR to find a solution.
When non-conductive materials slide, hit, peel, and rub; electrons from the surface can move from one atom to another; thus, creating static. The type of material and the amount of movement governs the amount of static forces. These strong static forces can attack debris and fibers, as well as generate shocks, misalignment, and machine jamming. Another feature of static is that it can regenerate if the materials continue to slide, hit, peel, and rub.
For the company above, they were printing on 30 cm by 48 cm (12” X 19”) PVC sheets. They used three different processes to print a complete credit card; silkscreen, digital, and offset. After each printing process, they would lose sections of the sheet due to poor image quality. At the end, they were losing between 20 to 30% in visual rejections.
For this application, we had to do two operations; remove the static and clean the surface from debris. The Gen4 Super Ion Air Knife can do both of these operations at the same time. With the laminar air stream that comes from the Super Air Knife, it can carry both positive and negative ions from the attached Gen4 Ionizing Bar. Together, they can remove any type of static charge as well as becoming a very effective tool as a non-contact wiper to remove debris. With this ability, the print quality would not be affected during cleaning. Since static is a surface phenomenon, I recommended to also remove the static from the other side of the sheets. We did not want to have any dirt or debris that could be remaining on the bottom surface to transfer from one surface to the next during stacking. This could scrape the finish during loading and unloading of the sheets.
I recommended two pieces of a model 112012 Gen4 Super Ion Air Knives that are manufactured to 12” (30 cm) in length. This customer can easily mount one above the sheet and one below the sheet prior to printing. To operate the attached Gen4 Ionizing Bar, EXAIR offers two types of power supplies, a two-output unit, model 7960, and a four-output unit, model 7961. They can save you money when needing multiple Static Eliminators to operate in your system. With a model 7960 Gen4 Power Supply, they now had a system to remove static and clean the sheets. Once they installed the Gen4 Super Ion Air Knives onto their system, the rejection rate dropped to near zero.
All EXAIR Gen4 Static Eliminators use one of two Power Supplies – your choice of the 2-port Model 7960, or the 4-port Model 7961.
Rejected parts are costly, wasteful, and reduce production rates. If you have rejection from static problems in your system, EXAIR has a large line of Static Eliminators to help you. You can contact an Application Engineer to review your application. For the customer above, the Gen4 Super Ion Air Knives made it possible to generate more credit cards per sheet.
EXAIR’sGen4 Super Ion Air Wipe provides a uniform 360 degree ionized air stream that clamps around a continuously moving part to eliminate static electricity and contaminants. It is ideal for removing dust, particulates and personnel shocks on pipe, cable, extruded shapes, hose, wire and more. This engineered product has undergone independent laboratory tests to certify it meets the rigorous safety, health and environmental standards of the USA, European Union and Canada that are required to attain the CE and UL marks. It is also RoHS compliant. New design features include a metal armored high voltage cable to protect against abrasion and cuts, a replaceable emitter point, integrated ground connection and electromagnetic shielding.
The Gen4 Super Ion Air Wipe uses a small amount of compressed air to entrain high volumes of ambient air. Two shockless ionizing points powered by our Gen4 UL Component Recognized 5kV Power Supply fills the air stream with static eliminating ions. That airflow impacts the surface of the material running through the air wipe and neutralizes the charge.
The Gen4 Super Ion Air Wipe, which compliments EXAIR’s complete line of Gen4 Static Eliminators, has an aluminum construction that is lightweight and easy to mount using the tapped holes provided. Two sizes include a 2 inch (51mm) diameter and a 4 inch (102mm). There are no moving parts to wear out. Visit EXAIR.com to see the entire Gen4 Static Eliminator product line and 1/2 inch through 11 inch Super Air Wipes for applications without static.
To discuss your application and how an EXAIR Intelligent Compressed Air Product can help your process, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
With the Gen4 Static Eliminators, EXAIR has added some great features and upgrades. In this video, I will show you how to replace the power rocker switch for the model 7960 and 7961 Power Supplies. Watch how to do it here:
